Flirting, or expressing sexual interest in someone is more than about the duration of the conversation, or even whether it's 1:1 or in a group.

That is very important. Simply talking to someone, and enjoying an extended, interesting conversation, is not by itself flirting or trying to pick someone up - if someone is interested, there's generally other body language, conversational clues, etc. If you feel that the encounter is going that way and you're not interested, then yes, backing off is polite. But I agree that you don't have a timer ticking - "Gee, I've been talking to them for 9.5 minutes. I have to run away now, or be willing to go out with them," or "Wow, a 20 minute conversation about the adaptation of the Hobbit movie! She wants me!"

If a guy, even at my age (24), came up to me and then kept coming back over and over to talk again of stayed talking with me for most of a party, I know my friends would notice and would ask if there was something going on - that seems reasonable to me as long as it was a question not an assumption. My answer however, wouldn't depend on the length of the conversation, but on the content and body language as blarg mentioned.

For example, I met up with a few friends and acquaintances from school. One of them is married and we got caught up in a very interesting conversation and did spend over an hour conversing with one another separately. No one watching would know that a great deal of that conversation was actually about how he met with his wife, her unique career, and him advising me about an interpersonal work problem I was having with his friend. Since we were meeting in a bar and everyone was drinking, it wouldn't surprise me if others did think there was flirtation happening just based on that, but neither him nor I walked away from that conversation thinking that it was more than a surprisingly interesting conversation with someone you previously only spoke with about super technical school information.

I agree it's not just the duration of the conversation, but in my mind that is one component of the whole picture. It's all about the verbal and non-verbal cues. If you are getting intersted or flirtatious vibes, then at the minimum they shouldn't be returned if there is no interest, but that also might suggest it's time to take a break from the conversation and mingle for a while.

I wanted to also add that some forms of "flirting" are not sexual at all and are neither intended nor typically interpreted as a signal that a person wants a romantic relationship. Some people are naturally flirtatious with nearly everyone.

I was recently "accused" by one of our secretaries of flirting with a sales rep who visited our department. The rep and I sat down to have about a 20 minute conversation in the office that mostly involved business and scientific topics. There was no personal aspect to it. Sales rep and I have known each other for about 5 years and are very comfortable with each other.

Secretary comes by afterwards with a sing-songy "Ooohh I saw you making eyes at him". My response was a confused "We were talking about [scientific thing]. Besides he's married and has grandchildren, I'm not interested." I guess I really didn't need to justify to her but it annoyed me nonetheless.

I agree it's not just the duration of the conversation, but in my mind that is one component of the whole picture. It's all about the verbal and non-verbal cues. If you are getting intersted or flirtatious vibes, then at the minimum they shouldn't be returned if there is no interest, but that also might suggest it's time to take a break from the conversation and mingle for a while.

Yup. If I'm happily engaged in a fun conversation with a new friend (especially if they seem well-intentioned but not entirely socially savvy) and I feel there's a question in their mind about the type of connection, I feel it's my responsibility to make sure to change the type of eye contact/shift body language/make a casual positive mention of DH/bring someone else into the conversation/etc. to clarify for them without needing to end our discussion. If they seem incapable of understanding the subtle cues, then I should be more directly proactive in redirecting.

Of course, a creep is a creep, but I'm not likely to catch myself sending signals that could easily be misinterpreted - such as an animated one-on-one discussion - to someone who I don't want to be around.

I agree it's not just the duration of the conversation, but in my mind that is one component of the whole picture. It's all about the verbal and non-verbal cues. If you are getting intersted or flirtatious vibes, then at the minimum they shouldn't be returned if there is no interest, but that also might suggest it's time to take a break from the conversation and mingle for a while.

Yup. If I'm happily engaged in a fun conversation with a new friend (especially if they seem well-intentioned but not entirely socially savvy) and I feel there's a question in their mind about the type of connection, I feel it's my responsibility to make sure to change the type of eye contact/shift body language/make a casual positive mention of DH/bring someone else into the conversation/etc. to clarify for them without needing to end our discussion. If they seem incapable of understanding the subtle cues, then I should be more directly proactive in redirecting.

Of course, a creep is a creep, but I'm not likely to catch myself sending signals that could easily be misinterpreted - such as an animated one-on-one discussion - to someone who I don't want to be around.

This has articulated everything I've wanted to say about this thread, but couldn't. Obviously, Ted was a creep and completely out of line for thinking a woman talking to him inherently implies sexual or romantic interest. And it's clear that Amy was not flirting with him.

However, I think it is wise to be aware of the signals others are sending you. So no, a long conversation with the opposite sex doesn't immediately signal interest. But it is one important component of signalling interest. So when one is in that situation, as Amy was, if you pick up on other components of flirtation or interest, I think it is a good idea to casually drop either one's boyfriend or lack of interest into the conversation, or to find someone else to chat with.

I think it's a little hyperbolic to suggest shock and outrage that someone of the opposite sex might think a long conversation would signal interest. I know that if a guy who was single spent an extended amount of time talking to me, I would probably wonder. Not feel that he was leading me on, obviously, but it would cross my mind that maybe he had an interest in me. And if I did not return that interest, I would signal it in some way. That is, in fact, exactly how I started dating the guy that I am seeing right now. We were at a group event, we spent most of the night talking, and that's how I knew he was interested. Spending long amounts of time talking to one person is a pretty common way when single of testing the waters, so to speak, of attraction.